The present invention is related to the field of valves which is ancient and widely known. A very simple valve may be comprised of an inlet channel, an outlet channel, and a moveable or deformable control element interposed between the channels. Movement or deformation (or both) of the control element regulates the transit of fluid from one channel to the other. The direction of fluid transit may be unrelated to nominal designations such as inlet and outlet, as is well known, or such designations may be chosen for reasons related to application such as in the case of a check valve intended to limit flow to only a preferred direction. Many valves have inlet and outlet channels which are formed as fluid conduits within portions of a valve body and a control element which is moved by an actuator (or the fluid itself) to changeable locations within a chamber of the valve. Controlled fluids may be liquids, gases, vacuum, vapors, or combinations of substances in those states. It is generally desirable to have most of the actuator not in contact with the controlled fluid. For example, a manual actuator having a knob for a person to grasp should avoid having the controlled fluid get on the person's hand. Many designs exist for allowing actuator movement while simultaneously retaining the controlled fluid within the valve chamber and sealingly separated from the actuator. Valves having actuators intended for simple on-off control of fluids as well as valves designed for proportional, or modulating, control of fluid delivery within industrial processes making semiconductor devices, pharmaceuticals, fine chemicals, and many similar fluid delivery systems, are well known.
Any fluid delivery apparatus intended for manipulating process materials within semiconductor manufacturing equipment usually requires attention to maintaining high purity of the delivered reactants. Mechanical shafts sliding or rotating within a packing type of seal arrangement are known to often cause detectable particulate contamination of high purity process materials. Fluids that are radioactive, poisonous, pyrophoric, or otherwise dangerous, may also be thought less safe when handled in an apparatus having packing type seals. In response to these concerns, designers developed valves whereby the actuator sealing is done by a flexible, usually metallic, element that separates the valve chamber from an external environment surrounding the valve. U.S. Pat. No. 3,278,156 issued to F. J. Callahan Jr., et al., is one example of a valve with a manual actuator using a metallic bellows for sealing the controlled fluid from the surrounding environment. Later experience revealed the relatively large surface area associated with the pleats of a bellows may be problematic with regard to internal sources of contamination in high purity fluid delivery systems. U.S. Pat. Nos. 4,606,374 and 4,732,363 both issued to Terrence J. Kolenc, et al, are two examples of valves using diaphragms, having fluid exposed surface area somewhat lower than bellows, for sealing and are also shown with manual actuators. A variety of actuator types, including pneumatic and electric, may be used with both bellows and diaphragm sealed valves, as is well known. The desire to absolutely minimize all possible moisture absorption sites within a high purity fluid delivery pathway has led to valve designs absent any internal polymeric material, and thus designs dealing with metal to metal contact between a moveable control element and a fluid conduit opening within the valve chamber. U.S. Pat. No. 5,730,423 issued to Jing-Chau Wu, et al., and U.S. Pat. No. 5,755,428 issued to Louis A. Ollivier are two examples of valves having metal diaphragms directly contacting a toroidal bead valve seat surrounding a fluid conduit opening within a valve body.